The invention relates generally to power-driven conveyors and, more particularly, to horizontal switches including conveyor belts with selectively rotatable rollers useful in diverting conveyed articles to selected positions across the width of the belt.
In the package-handling industry, switches are used to merge, divert, or sort packages or articles received from one or more infeed conveyors and discharged onto one or more output conveyors. In a typical sorting application, as illustrated in FIG. 20, a switch 20 sorts articles 22 received from an infeed conveyor 24 by selectively diverting individual articles to one or the other of two parallel outfeed conveyors 26, 27. Shoe sorters are often used as sorting switches in this application.
One typical shoe sorter switch includes an endless conveyor belt or chain constructed of a series of slats flanked by drive chains. Another typical sorter includes rods uniformly spaced between parallel drive chains. A shoe for pushing articles across the sorter is movably attached to each slat or between consecutive rods. Typically, the shoe has an appendage that extends downward of the slat or between the rods. A guide track arrangement in the conveyor frame beneath the conveyor guides the shoes across the conveyor as it is driven in the conveying direction. The specific arrangement of the guide track programs the system to push conveyed articles to specified lateral positions on the sorter.
But these chain-driven sorting switches have shortcomings. One shortcoming is that their construction limits the placement of connecting joints between consecutive slats or rods because of interference with the shoes and associated appendages. For that reason, the slats or rods can sag in the middle because they are supported mainly at the drive chains positioned out of the shoe's travel range at the side edges of the slats. This problem is especially noticeable on wider conveyors. Another shortcoming is that the shoe mechanisms and the guide track arrangement can be complex and, consequently, expensive.
Roller conveyors are also used as shoe sorters in many applications, especially for heavy articles, such as tires, and also for beverage cases and for low-profile, multi-sized articles, such as packages and mail. But one of the problems with roller conveyors is that these metal conveyors can be noisy, especially as their bearings wear. Frequent maintenance operations, such as lubricating and tightening, and repairs are a way of life with roller conveyors.
Thus, there is a need for a conveyor that can sort and divert conveyed articles, such as cases and packages, but without the shortcomings of shoe sorters or roller conveyors.